Text 1: The Periodic Table and the Periodic Law

The story of how D. I. Mendeleyev established the Periodic System of Elements has long been a matter of great interest to research workers¹.

When Mendeleyev began to teach at St. Petersburg University, chemistry was still far from being the well-ordered² and harmonious branch of science that we know today.

The great majority of scientists were firmly convinced that atoms of different elements were in no way connected with each other, and that they were quite independent particles of nature. Only a few advanced scientists realized that there must be a general system of laws which regulates the behaviour of atoms of each and every element. However, the few attempts made by Beguyer de Chancourtois, Newlands, Lother Meyer and others to find a system of laws controlling the behaviour of atoms were unsuccessful and exercised no influence³ on Mendeleyev, the future founder of the Periodic System of Elements.

"Mendeleyev was a man who could not bear any kind of disorder and chaos," writes Academician A. A. Boikov. "This is why at the beginning of his course in chemistry at St. Petersburg University, where he had been appointed to the department of chemistry, D. I. had to establish the order in the chemical elements."

By comparison⁴ of chemical properties of different elements researchers had long ago discovered that elements could be placed in several groups according to similarity⁵ in their properties.

Mendeleyev applied in his system the principles that he developed and included in his table the listing of the elements according to increasing weights.

Because he had the insight to see that many elements had not yet been discovered, he left open spaces in the Periodic Table. For example, he predicted⁶ that an unknown element with atomic weight of 44 would be found for the space following calcium. And in 1879 the Swedish chemist Lars Fredric Nilson discovered scandium⁷.

Mendeleyev's table developed into the modern Periodic Table is one of the most important tools in chemistry. The vertical columns of the modern Periodic Table are called groups and the horizontal rows are called periods. The atomic number of an element is the number of protons in the nucleus of the atom of that element. The modern Periodic Table not only clearly organizes all the elements, it lucidly⁸ illustrates that they form "families" in rational groups, based on their characteristics.

1research worker – дослідник, вчений 2well-ordered – упорядкований 3influence - вплив 4comparison – порівняння

5similarity – схожість 6to predict – передбачати 7scandium – скандій 8lucidly – зрозуміло,

Ex. 5. Look through the text again and find the sentences where the author describes the following facts:

1. Mendeleyev could foresee the existence of new elements because he was very gifted.

2. Scientists of Mendeleyev's time didn't believe that elements are connected with each other.

3. Mendeleyev's character made him order the elements.

4. Mendeleyev's work on the Periodic Table and the Periodic Law has long interested scientists.

5. There were some scientists' attempts to find a system to order the elements but they failed.

6. Thanks to Mendeleyev modern chemistry uses the clearly developed Periodic System as the main instrument.

Ex. 6. Answer the following questions choosing the correct answer out of the given ones:

1. Where did Mendeleyev start ordering the elements?

1. at school;

2. at St. Petersburg University;

3. abroad.

2. Why did Mendeleyev turn to ordering the elements? Because:

1. other scientists' attempts failed;

2. he had a talent;

3. he didn't like disorder.

3. What did the researchers try to do to find some order of the elements?

1. they compared different properties;

2. they read scientific literature;

3. they denied the earlier attempts of the scientists.

4. How did Mendeleyev list the elements?

1. according to their names;

2. according to their atomic weights;

3. according to their chemical symbols.

5. What did scientists of Mendeleyev's time think about atoms of different elements?

1. they were independent particles of nature;

2. they were closely connected;

3. they belonged to a well-ordered system.

Ex. 7. Find in the text all the sentences containing the sequence of tenses. Translate them into Ukrainian.

Ex. 8. Translate the following sentences into Ukrainian.

1. The scientist said that our age was the age of chemistry. 2. The ancient Greek philosophers thought that matter consisted of infinitely small particles. 3. Aristotle believed that his theory would agree with the general views on nature. 4. After Copernicus and Galileo everybody could know that the Earth turns round the Sun. 5. Cavendish discovered that water consists of a definite proportion of hydrogen and oxygen. 6.Few scientists of that time knew that Mendeleyev had discovered the Periodic System of Elements.7. It was reported that those interesting experiments would initiate a series of similar investigations. 8. The professor said that they had found some unknown properties of that substance. 9. It was reported that the new element would occupy the definite place in the Periodic Table. 10. They assumed that their method of investigation could be applied in many experiments.

Ex. 9. Translate the following sentences into English.

1. Професор сказав, що цей експеримент проводиться для ілюстрації його доповіді. 2. Студенти сказали, що дізналися про нове відкриття на семінарі. 3. Викладач знав, що декілька студентів стануть дослідниками. 4. Вчені були впевнені, що деякі відкриття вплинуть на наукові погляди Менделєєва. 5. Декілька прогресивних вчених розуміли, що існує визначена система елементів. 6. У своїй книзі Б. Н. Конарев доказує, що в стародавності люди знали тільки ті речовини, які були їм необхідні для життя. 7. Арабські алхіміки вже в IX-X ст. вважали, що всі речовини можна розділити на органічні та неорганічні. 8. Лавуазьє відповів на ті питання, на які не могли знайти відповіді вчені кількох поколінь. 9. Викладач розповів на лекції, який внесок зробив Берцеліус у неорганічну хімію. 10. Ми знаємо, що Берцеліус був автором декількох підручників з хімії.

Ex. 10. Before reading the text find the explanation of the following words.

1	air	A	action taken beforehand to avoid risk or ensure a good result
2	current	B	colourless transparent liquid compound of oxygen and hydrogen.
3	material	C	a gas into which water is changed by boiling
4	precaution	D	matter from which a thing is made
5	steam	E	any of the limits of a solid
6	surface	F	an ordered movement of electrically charged particles
7	water	G	mixture mainly of oxygen and nitrogen surrounding the earth